• Steven Rostedt's avatar
    x86: Keep current stack in NMI breakpoints · 228bdaa9
    Steven Rostedt authored
    We want to allow NMI handlers to have breakpoints to be able to
    remove stop_machine from ftrace, kprobes and jump_labels. But if
    an NMI interrupts a current breakpoint, and then it triggers a
    breakpoint itself, it will switch to the breakpoint stack and
    corrupt the data on it for the breakpoint processing that it
    interrupted.
    
    Instead, have the NMI check if it interrupted breakpoint processing
    by checking if the stack that is currently used is a breakpoint
    stack. If it is, then load a special IDT that changes the IST
    for the debug exception to keep the same stack in kernel context.
    When the NMI is done, it puts it back.
    
    This way, if the NMI does trigger a breakpoint, it will keep
    using the same stack and not stomp on the breakpoint data for
    the breakpoint it interrupted.
    Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    228bdaa9
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